The relationship between the development of vision and the development of eye movements is a reciprocal one: each affects the other. Oculomotor disorders (e.g. strabismus and nystagmus) can have marked, deleterious effects on the development of vision. Although there is a body of literature concerning the development of vision, very few quantitative data are available about the development of eye movements. Our overall objective is to carry out a quantitative analysis of the developmental roles of vestibular, smooth pursuit and optokinetic eye movement systems in maintaining a stable image on the retina for visual processing during head movements in infants and young children. The data should provide clinicians a better understanding of how oculomotor disorders influence the development of vision in young infants. Specific Aims 1. To quantify the developmental changes in the gain of the vestibulo-ocular (VOR) reflex in the dark. 2. To study the interaction of the VOR with the SP and OK mechanisms by measuring the gain of the compensatory eye response as the infant (a) fixates a stationary target during a head movement and (b) tracks a stimulus moving with its head. 3. To quantify the evaluate the development of the SP and OK systems in conditions similar to those used to evaluate the visual- vestibular interactions. 4. To chart, longitudinally and quantitatively, the changes in these different movement responses to determine whether there is a coordination among them which leads to optimal compensatory eye responses throughout development.